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This study critically discusses the fundamental concepts used for evaluating the flexural and axial resistance of structures under blast. Simplified methods based on single degree of freedom are emphasized. The paper begins with how to estimate the blast parameters for a given charge size and standoff distance. These parameters include side-on and reflected pressures, positive phase duration, and side-on and reflected impulses. Subsequently, blast damage criteria are defined in accordance with prevailing guidelines and some of their short comings are discussed. To assess the impact of blast on the flexural safety and performance of structures, some simple methods are presented. The methods are either empirical or are based on the principles of energy and momentum conservation. The analytical results are in closed-form or in the form of pressure–impulse (P–I) diagrams. The effect of strain rate on both blast-induced flexural deflection and strength of structures, with particular emphasis on reinforced concrete structures, is discussed.

In this study, the dynamic response of typical wide-flange steel beams was experimentally evaluated under blast loading. A total of 13 beams were field tested using live explosives, where the charge size ranged from 50 to 250 kg of ammonium nitrate-fuel oil mixture, and the ground stand-off distance was from 7.0 to 10.3 m. Blast wave characteristics, including incident and reflected pressures, were recorded. In addition, time-dependent displacements, accelerations, and strains at different locations along the steel members were measured, and the postblast damage and mode of failure of the test specimens were observed. The blast load characteristics were compared with those obtained using the Technical Manual UFC 3-340-02 results. The displacement response results were used to validate the results obtained from a nonlinear dynamic analysis based on a single degree-of-freedom (SDOF) model. Results showed that the UFC 3-340-02 pressure predictions compare reasonably well with the measured pressure in the positive phase in terms of both the peak pressure and overall time variations. The SDOF model predicted the maximum displacements of beams in the elastic range reasonably well, but it overestimated them in the plastic range.

The increasing tendency to use urban civilian buildings for military purposes prompts the need for the assessment of their blast resistance. Many of these buildings are made of reinforced concrete (RC). Popular tools available for the assessment of existing RC structures in practice include guidelines and design standards, technical manuals and specialised software. These tools include certain assumptions based on scarcely available test data, as historically they were collected for military purposes. Efforts to transfer this knowledge from military to civilian applications are relatively recent and need be corroborated by further testing and numerical analysis. The objective of this paper is to present the results of field tests on full-scale RC members to check the validity of a number of assumptions routinely made in current numerical/analytical models. The data captured during the tests, including reflected pressure and member displacements, are compared with results of empirical and numerical models, in order to gauge the robustness and accuracy of the assumptions underpinning these models. Finally, recommendations are made for an expedient assessment of existing buildings based on simple methodologies.

Past research indicates that red mud (RM) has negligible pozzolanicity unless calcined. An iron-rich and silicate-poor RM was calcinated at 600, 800 and 1000 °C to investigate this issue. Tests were performed on mortars made with Portland cement (control) and with 85 wt% cement and 15 wt% RM. At 91 days, the mortar containing non-calcined RM reached 94% of the compressive strength of the control mortar, but the ones containing calcined RM attained much lower strength. Mineralogical, microstructural, and thermodynamic analyses are performed to find the mechanisms undergirding this behavior. The crucial influences of Al/Si ratio and crystalline transformations are highlighted.

Shrinkage cracks in Portland cement concrete can cause serious problems when cracked reinforced concrete is subjected to corrosive agents such as salts. The seepage of salty solutions through the cracks into the reinforcing steel can lead to corrosion of the steel and ultimately failure of the structure. This paper presents the results of an extensive experimental investigation designed to evaluate the potential of using polymer grids to minimize shrinkage cracks and their subsequent effects on corrosion of steel reinforcement. The investigation consisted of a short-term and a long-term programme. In the short-term programme, 120 × 600 × 2000 mm concrete slabs were subjected to drying shrinkage. In the long-term programme, 100 × 500 × 3200 mm concrete slabs were loaded and unloaded under severe conditions of deicing salt applications. The test results showed that the use of polymer grids can minimize shrinkage cracking. Also, in the occurrence of a crack, the presence of polymer grids as secondary reinforcement resulted in controlling the crack width.

Canadian research on FRP applications in construction is described. The research is carried out mainly in Canadian universities, or in some Canadian federal government laboratories, and is focused on the design, construction, and repair/strengthening of reinforced concrete structures. The research on new structures focuses primarily on bridges, particularly on bridge decks, while research related to repair/strengthening involves bridges and buildings. The FRP of choice in Canada is CFRP, with some research involving GFRP. The research results have led to the development of FRP design codes for both buildings and bridges and to a number of demonstration projects and field applications. To date, two highway bridges have been constructed in Canada in which some of the bridge girders are prestressed with CFRP tendons. In addition, a number of other bridges have been constructed where the deck slab and barrier walls have been partially or entirely reinforced with CFRP or GFRP bars. CFRP sheets and laminates have been used to repair/strengthen concrete structures for increased flexural, axial, and shear strength.

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Carbon nanotubes (CNT) as a functional filler can increase the electrical conductivity property of concrete and thus provide intrinsic self-sensing properties with no need for external sensors to monitor the behavior of concrete infrastructure and structures containing CNT. CNT-cement composites also improve mechanical strength and have higher energy absorption capacity. The sensitivity of their electrical conductivity to external physical parameters, such as strain, stress, load, temperature, displacement, and pressure, makes them suitable for structural health monitoring (SHM) applications. This paper presents a comprehensive review of the CNT properties, fabrication process, composition, and sensing characteristics as well as challenges for applying CNT concrete as part of a self-sensing structure. Furthermore, the self-healing property of CNT, as an integral feature of future smart concrete infrastructure is discussed.

To reduce the heat loss from the PCM Trombe wall and increase its thermal efficiency, an innovative dynamic Trombe wall incorporating a PCM layer on one face and an insulation layer on the opposite face is proposed. During the charging period of the PCM, the face containing the PCM is exposed to solar irradiation, while the face containing the insulation is exposed to the conditioned air. During the discharging period, the two faces exchange position. A large-scale model of a building unit with such a wall is constructed and tested. The model is analyzed using three-dimensional computational fluid dynamics (CFD), with generally good agreement between the two sets of results. Subsequently, CFD models of three building units are analyzed, one having the proposed dynamic wall, the other an analogous static wall, and the last one identical to the static wall but without PCM. Throughout the PCM discharging period, the temperatures of all the surfaces and the air in the conditioned space in the unit with the proposed wall are found to be consistently higher than those in the companion units. Based on energy conservation analysis, compared with the static wall, with and without PCM, the energy saving efficiency of the proposed wall is higher 25.3% and 17.5%, respectively. Similarly, its thermal efficiency is higher 79.8% and 35.4%, respectively. To achieve even higher thermal efficiency, it is shown that the thermal resistance of the glazing in the envelope, and the envelope as a whole, need to be increased by using materials with low density and heat capacity.

In some regions concrete is partially frozen for several months each year, yet there is paucity of information about the effect of air entrainment on chloride diffusivity and binding in partially frozen concrete. To address this issue, concrete without and with entrained air were subjected to chloride diffusion under constant exposure temperatures of +5, 0, −5, and −15 °C and their total and free chloride concentrations were determined. The entrained air reduced chloride diffusivity by 18% when the concrete evaporable water was either unfrozen or nearly fully frozen, but when it was partially frozen it reduced it by only 3%. Non-air entrained concrete exhibited higher binding capacity than air entrained concrete under all the test temperatures. After freezing, the effect of temperature on concrete diffusivity cannot be captured by Arrhenius law alone. A procedure is proposed to account for this deviation and the predicted diffusion coefficients agree reasonably with the experimental values.

In this study the concepts of reliability are used to derive blast load factors. First, some objective criteria are proposed for the proper interpretation of pressure data gathered in arena tests. These criteria are applied to the pressure–time histories recorded during field tests involving live explosive detonated in contact with the ground. Three major shock wavefront parameters, including peak pressure, impulse, and positive phase duration are calculated. Next, statistical analysis is performed on these metrics to estimate their probability density functions and goodness-of-fit tests are carried out to gauge the appropriateness of each estimate. Using the best-fitting distribution for each wavefront metric, load factors are derived on the basis of two approaches. The first approach employs the percentiles of the three load metrics, each estimated using the pertinent probability distribution. The second approach uses concepts of reliability and presents load factors for low, medium, and high level of protection. The two sets of load factors are compared and the limitations of each approach are discussed.

Calcium sulfoaluminate cement concrete (CSAC) reinforced by fiber-reinforced polymer (FRP) bars, termed bars for brevity, is a good alternative to steel-reinforced concrete in marine environments due to the corrosion resistance of FRP and the lower pH of CSAC. For the first time, multi-mechanical tests are conducted to compare the durability of glass FRP (GFRP) to that of carbon FRP (CFRP) after exposure to CSAC pore solution. The bars were immersed in a simulated pore solution of CSAC made with either fresh water and river sand or with seawater and sea sand. Solution temperature was held constant at 30 °C, 45 °C or 60 °C for 30, 60, 90 and 180 days of immersion. Tensile, horizontal and transverse shear tests, as well as detailed microstructural analyses, were conducted to determine the level and mechanisms of degradation for each type of bar. Sea salt increases the degradation of both bars, but it degrades GFRP more than CFRP. The bars’ retained tensile strength is a reliable indicator of their durability, while their post-exposure horizontal and transverse shear strengths are found inconsistent and counter intuitive. In the GFRP, the fiber, the epoxy matrix and their interface suffered damage, but in the CFRP, the carbon fiber was not damaged. Under the test conditions in this study, the maximum reduction in the tensile strength of the GFRP was 56.9% while that of CFRP was 15.1%. Based on the relevant ASTM standard, the CFRP bar satisfies the alkaline resistance requirement of the standard in the CSAC pore solution with and without salt, whereas the GFRP bar does not meet the same requirement in the above pore solution with salt.

Membrane distillation (MD) is a thermally driven separation process that is driven by phase change. The core of this technology is the hydrophobic microporous membrane that prevents mass transfer of the liquid while allowing the vapor phase to pass through the membrane's pores. Currently, MD is challenged by its high energy consumption and membrane degradation due to fouling, scaling and wetting. The use of electrically conductive membranes (ECMs) is a promising alternative method to overcome these challenges by inducing localized Joule heating, as well as mitigating and monitoring membrane fouling/scaling/wetting. The objective of this review is to consolidate recent advances in ECMs from the standpoint of conductive materials, membrane fabrication methodologies, and applications in MD processes. First, the mechanisms of ECMs-based MD processes are reviewed. Then the current trends in conductive materials and membrane fabrication methods are discussed. Thereafter, a comprehensive review of ECMs in MD applications is presented in terms of the different processes using Joule heating and various works related to membrane fouling, scaling, and wetting control and monitoring. Key insights in terms of energy consumption, economic viability and scalability are furnished to provide readers with a holistic perspective of the ECMs potential to achieve better performances and higher efficiencies in MD. Finally, we illustrate our perspectives on the innovative methods to address current challenges and provide insights for advancing new ECMs designs. Overall, this review sums up the current status of ECMs, looking at the wide range of conductive materials and array of fabrication methods used thus far, and putting into perspective strategies to deliver a more competitive ECMs-based MD process in water treatment.